Experimental cookery

Effect of inert gases and humidity. Triebold and Bailey found that crackers as well as fats stored in an atmosphere of COo were as rancid as control samples stored in air. Other investigators have also reported the ineffectiveness of COo in retarding the development of rancidity. However, storage in an atmosphere of nitrogen or hydrogen retards the development of rancidity. Triebold and Bailey also found that zero-per cent relative humidity favors, but some humidity retards, oxidative rancidity. However, humidity as high as 50 to 75 per cent produces mustiness. The 5- to 6-per cent moisture content of crackers aids in keeping the crackers fresh. They also found that in general the keeping quality of crackers was related to the length of the induction period of the shortenings used in them, but several outstanding exceptions to this relationship were noted, so that the keeping quality was more closely related to the induction period of the crackers themselves. Antioxidants for fats in contact with water. Lea was interested in find- ing antioxidants for bacon fat. He investigated the effect of different sub- stances on fat in contact with a brine pickle. His results follow. Oxidation of lard in a glass vessel in contact with water is much more rapid at an alkaline than at an acid />H. It is suggested that this is due to dissolution of copper from the glass. At a /»H below 5, nitrate is a powerful accelerator. Copper and iron in aqueous solution accelerate the oxidation of lard, copper being approximately 20 times as active as iron. Copper was active in as low concentrations as 0.01 p. p.m. Aliphatic polyhydroxy-compounds such as glycerol and the sugars are weak antioxidants. Aliphatic hydroxy-acids, e.g., lactic and glycoUic, the ethanolamines and maleic acid are moderate, and polybasic hydroxy-acids, e.g., tartaric and citric, are powerful anti- oxidants. Aliphatic amino-acids, e.g., glycine, aspartic and glutamic acids, and asparagine are all powerful antioxidants. Protein has considerable antioxidant activity and may be partly responsible for the stabilization of EFFECT OF LIGHT, HEAT, AND AIR 553 crude natural oils and fats. The prooxidant effect of copper at low con- centrations (up to approximately 1 p.p.m.) is completely inhibited by protein and other antioxidants. At higher concentrations of the metal, even 4 per cent of protein fails to prevent a powerful acceleration of oxidation. Orthophosphoric acid is a fairly good, and pyrophosphoric a very good, antioxidant. Phosphorous acid is also effective. These water-soluble anti- oxidants still retard oxidation when the water content is as low as 0.25 per cent. They are active at />H 7, certainly in more acid and probably in more alkaline solutions. Volatilization of rancid products. Roschem and Newton found that samples of rancid lard blown with steam at 100°C. were odorless, bland- tasting, and entirely palatable, i.e., the products causing the rancid flavor and odor were volatile. Furthermore these volatile substances had no accelerating effect in oxidation of lard. This was interpreted to mean that the accelerating effect is due to a substance or substances of heavy molecular weight not volatile, with steam distillation at 200°C. and 3 to 5 mm. mercury pressure.